Lithium-ion batteries, nickel-metal hydride batteries, and other secondary batteries have become more important recently as a vehicle-mounted electrical power source, as well as a power source for personal computers and portable devices. In particular, it is expected that lithium secondary batteries, which offer both light weight and high energy density, can be preferably used as a high output electrical power source for vehicles. One typical configuration for such a secondary battery provides an electrode with a configuration in which a material capable of reversibly absorbing and desorbing lithium ions (electrode active material) is retained on a conductive material (electrode current collector). A typical example of an electrode active material used in a negative electrode (negative electrode active material) is a carbon material such as graphite carbon or amorphous carbon. Moreover, a typical example of an electrode current collector used in a negative electrode (negative current collector) is a sheet-shaped or foil-shaped material containing mainly copper or a copper alloy.
When manufacturing a negative electrode having such a configuration, a typical method for retaining the negative electrode active material on the negative current collector involves dispersing a powder of the negative electrode active material and a binder in a suitable dispersant to prepare a mixed material paste, forming a layer containing the negative electrode active material (negative electrode mixed material layer) by applying the paste to the negative current collector (copper foil, etc.), and then drying the same by passing it through a hot air dryer. In this case, the binder in the negative electrode mixed material layer performs the role of binding the particles of negative electrode active material together and binding the negative electrode mixed material layer to the negative current collector. Furthermore, the binder in the negative electrode mixed material layer acts to bind the negative electrode mixed material layer to the negative current collector. Patent Documents 1 to 5 can be noted as technical documents relating to the manufacture of this type of electrode.